Process of separating alkali-metal sulfates from mixed solutions.



UNITED STATES NICE. 1

ATE T oARL HoEPENER, oE ERA'NKEoRT-oN-TnE-MAIN, GERMANY; HENRY ORTI-I,

JR, ADMINISTRATOR or SAID HOEPFNER, DECEASED.

PROCESS OF SEPARATING ALKALl-METAL SULFATES FROM MIXED SOLUTIONS.

SPECIFICATION forming part of Letters Patent N 0. 704,036, dated July 8,1902.

Application filed September 2 7, 1 89 9.

To all whom, may concern:

Be it known that I, CARL HOEPFNER, a subject of the Emperor of Germany,residing at Frankfort-on-the-Main, Germany, have invented certain newand useful Improvements in Processes of Separating Alkali-Metal Sulfatesfrom Mixed Solutions; and'I do hereby declare the following to be afull, clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

This invention relates to the separation of alkali-metal sulfates frommixed solutions.

' I have found that in the practical leaching of ores of zinc andsimilar metals with sulf urous or sulfuric acids and in the subsequentconversion of the resulting sulfate or sulfite.

into a chlorid by means of a chlorid of an alkali metal with thesimultaneous formation of an alkali-metal sulfate by doubledecomposition it was a very difficult matter to separate the zincchlorid from the alkali-metal sulfate, especially when concentratedsolutions of salts were used.

Heretofore it has been impossible to separate the alkali metal sulfatecontained in concentrated solutions, together with zinc and similarmetals, by cooling, because such cooling was gradual and resulted in thecrystallizing out of a double sulfate of the alkali and a metal, in thecase of zinc with the formation of ZnSO ,Na SO from which the recoveryof zinc is difficult. I have found that when mixed solutions of suchsalts are cooled rapidly or suddenly, and especially with concentratedsolutions, the metal is not precipitated, but only the sulfate of thealkali metal. I cool these mixed solutions-rapidly by allowing them toflow into a solution of a chlorid, as NaOl or ZnCl which contain fromten per cent. to twenty per cent. of sodium chlorid and from ten percent. to twenty per cent. of zinc in the form of chlorid or a mixture ofboth constantly stirred and kept cold below Serial No. 731,853. (Nospecimens.)

suitable cooling medium, as ammonia from an ice-machine circulating inpipes around or through the vessel containing the chlorid bath. Themixed sulfate solution is thus ble fluctuations of temperature of bathand variations in concentrations. The chlorid solutions are drawn offfrom time to time and the alkali-metal sulfate crystals removed, or theymay be shoveled from the bath from time to time.

In the process of cooling it is of course necessary tohave arefrigerating-machine, and in such it is customary to cool the expandedgases by means of water, which will reduce their temperature toapproximately 10 centigrade. In order to still further cool them, Ipropose to use the cold solutions containing metals after the alkalinesulfate has been separated. Y 1

Having thus described my invention, what I claim as new therein, anddesire to secure by Letters Patent, is

1. The method of separating alkaline sulfates from mixed solutions,which consists in rapidly cooling the same by allowing them to flow intoa cold solution of a suitable chlorid, thereby preventing the formationof double salts, substantially as set forth.

2. The method of separating alkaline sulfates from mixed solutions,whichconsists in rapidly cooling the same by allowing them to flow intoa suitable cold chlorid solution while being constantly stirred,substantially as set forth.

3. The method of separating alkali-metal sulfates from mixed solutionsof high concentration, which consists in rapidly cooling the same byallowing them to flow into a cold solution of a suitable chlorid whilebeing constantly stirred, substantially as set forth.

4. The method of separating alkaline sulfates from mixed'solutions,which consists in ICO rapidly cooling the same by allowing them to myinvention I have signed myname in presflow into a cold solution of achlorid While ence of two subscribing witnesses. being constantlystirred, using the resulting cold solution to reduce the temperature ofCARL HOEPFNEP 5 cooling-gases used in the refrigerating plant,Witnesses:

substantially as set forth. THOS. H. YOUNG, In testimony that I claimthe foregoing as HENRY ORTH, Jr.

